Effect of pH and temperature

The fact that cellulase adsorbs onto its substrates and the action has a fractional reaction order has important effects on such practical issues as the pH and temperature ranges. 

If one measures the enzyme activity as a function of pH or temperature using a soluble substrate, such as hydroxyethyl cellulose, one obtains curves characteristic of many enzymes. The temperature curve follows an Arrhenius dependence at temperatures leading up to the optimum, then drops sharply at inactivating temperatures (Fig. 1). The pH curve is roughly a bell shape, with the optimum spanning 1 to 3 pH units (Fig. 2). This exercise gives a first estimate of the pH and temperature curves, but often the behavior in specific applications is quite different. 

Because the enzyme adsorbs to its substrate, the nature of the substrate influences the activity profiles. For example, as the pH is varied, the charge of the substrate and particularly ionic components of the substrate will change. This can effect the enzymes activity. For this reason, pH and temperature profiles for a given enzyme can vary widely among substrates. 

The fractional reaction order dependence of the extent of reaction on enzyme dosage will tend to flatten the profiles observed in actual applications. For example, if an enzyme has a reaction order of 0.5 in a given application, then a 

4 X change in enzyme activity (caused by a change in temperature) will only cause a 2 X difference in the amount of enzyme action. Therefore, a graph of enzyme action as a function of temperature will have a flatter profile than a graph of enzyme activity as a function of temperature. 

The fructosyltransferase from A. aculeatus displayed activity without the addition of any metal ions. However, some effects were observed in its susceptibUity to mono- and divalent cations [33]. For ejample, Mn, K, and Co caused a 1.4—1.9-fold increase in the activity, whereas low concentrations of Hg and Zn produced 35-60% inhibition. It was also found that the enzyme was slightly activated by several non-ionic and anionic surfactants such as sodium dodecylsulphate (1.5-fold at lOmM), sodium deoxycholate (1.4-fold at ImM), and Triton X-100 (1.4-fold at 5% w/v). Moreover, it was resistant to low concentrations (1-lOmM) of reducing agents such as dithiothreitol and P-mercaptoethanol. 

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Oplopborus luminescence, 82-87 effects of pH and temperature, 83-86 luminescence spectrum, 84 mechanism, 85-87 quantum yield of coelenterazine, 85 Orfelia, 2, 27, 337... 

Brownson JRS, Georges C, Larramona G, Jacob A, Delatouche B, Levy-Clement C (2008) Chemistry of tin monosulfide (8-SnS) electrodeposition effects of pH and temperature with tartaric acid. J Electrochem Soc 155 D40-D46... 

Zinc sulfide, with its wide band gap of 3.66 eV, has been considered as an excellent electroluminescent (EL) material. The electroluminescence of ZnS has been used as a probe for unraveling the energetics at the ZnS/electrolyte interface and for possible application to display devices. Fan and Bard [127] examined the effect of temperature on EL of Al-doped self-activated ZnS single crystals in a persulfate-butyronitrile solution, as well as the time-resolved photoluminescence (PL) of the compound. Further [128], they investigated the PL and EL from single-crystal Mn-doped ZnS (ZnS Mn) centered at 580 nm. The PL was quenched by surface modification with U-treated poly(vinylferrocene). The effect of pH and temperature on the EL of ZnS Mn in aqueous and butyronitrile solutions upon reduction of per-oxydisulfate ion was also studied. EL of polycrystalline chemical vapor deposited (CVD) ZnS doped with Al, Cu-Al, and Mn was also observed with peaks at 430, 475, and 565 nm, respectively. High EL efficiency, comparable to that of singlecrystal ZnS, was found for the doped CVD polycrystalline ZnS. In all cases, the EL efficiency was about 0.2-0.3%. 

Effect of pH and temperature on the purified enzyme activity and stability The conditions of the enzyme activity and the stability was done followed Buranakarl, et al. (16). 

Effect of pH and temperature on the purified enzyme activity and stability... 

Given an estimate of the time to completion and precision of the analysis, one can temporarily eliminate time as a variable and construct an analysis of variance (ANOVA) to examine the effects of pH and temperature. A simple ANOVA would consist of four groups, with several replicates in each group, as shown in Table 4. 

From an isotherm test it can be determined whether a particular organic material can be removed effectively. It will also show the approximate capacity of the carbon for the application and provide a rough estimate of the carbon dosage required. Isotherm tests also afford a convenient means of studying the effects of pH and temperature on adsorption. Isotherms put a large amount of data into concise form for ready evaluation and interpretation. Isotherms obtained under identical conditions using the same contaminated groundwater for two or more carbons can be quickly and conveniently compared to determine the relative merits of the carbons. 

To study the effect of pH and temperature, 0.25 ml of the lignin peroxidase diluted with water was mixed with 0.75 ml of buffer, pH 3.0 - 7.0 and incubated at temperatures of30- 70°C. The protein concentration of the incubation mixture was 50 ig/ml. After various incubation times (0 - 27 h) the inactivation was stopped by adding 9 ml of cold 0.33 M tartrate buffer, pH 3.0. 

Figure 13 Effect of pH and temperature on malathion degradation by hydrolysis (temperature in degrees C) degradation is faster at higher temperatures and pH values further away from 4.0 to 4.2 (from Ref. 11).

Nagano,T Nakashima, S. Nakayama, S. Se-noo, M. (1994) The use of color to quantify the effects of pH and temperature on the crystallization kinetics of goefhite under highly alkaline conditions. Clays Clay Min. 42 226-234... 

Hagenmaier (10) demonstrated that pH had little effect on water absorption of oilseed protein products, but solubility was pH dependent. He suggested that the differing degree of dependence on pH indicates that water absorption and protein solubility are not correlated. Contrastingly, Wolf and Cowan (28) reported the pH-water retention curve of soy proteins to follow the pH-solubility curve. Both solubility and water retention were minimal at the isoelectric point (4.5) and increased as the pH diverged from this point. Hutton and Campbell (20) reported that the effects of pH and temperature on water absorption of soy products paralleled those of solubility for the most part. 

E. Other Factors Affecting Activity 1. Effect of pH and Temperature... 

H. Einarsson, The effect of pH and temperature on the antibacterial effect of Maillard reaction products, Lebensm. Wiss. Technol., 1987, 20, 56-58. 

Figure 7.17. Effects of pH on binding of phosphofructokinase (PFK) to myofibrils (open symbols dashed line) and interacting effects of pH and temperature on the self-assembly of PFK, as indexed by residual PFK activity (filled symbols solid lines). Binding of PFK to myofibrils was measured using PFK-con-taining supernatants and myofibrillar preparations from white locomotory muscle of the teleost Paralabrax nebulifer (Roberts et al., 1998). PFK self-assembly was studied using purified enzyme from a mammal (Spermophilus beecheyi) (Hand and Somero, 1983). The percent residual PFK activity after incubation for 60 min under different combinations of pH and temperature provides an estimate of the fraction of PFK that remains as catalytically active tetramers or aggregates of tetramers. (Figure from Somero, 1997.)...

Jiang F, Kongsaeree P, Schilke K et al (2008) Effects of pH and temperature on recombinant manganese peroxidase production and stability. Appl Biochem Biotechnol 146 15-27... 

Although it is a simple matter, experimentally, to determine the characteristics of the movement of a particular compound across a membrane (e.g., the effect of pH and temperature on the rate), it is difficult to examine how a carrier operates at a molecular level. 

Fio. 11.—Effect of pH and temperature (T) on the formation of the amylose-iodine complex, expressed as the change (in %) of the relative extinction of the band measured at 625 nm. (Reprinted with permission from J. Hollo and J. Szejtli, Przem. Spoz., (1957) 429-433.)... 

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